Leonard will play Roger Kadar, PhD, an obsessive and gifted scientist who runs Charleston’s power grid. He lives underground with his pet rats and cool science toys, leading the children of the newfound haven to dub him The Rat King.

Additionally, Gloria Reuben will reunite with her ER costar Noah Wyle in a five-episode stint as Tom Mason’s (Wyle) aide, who is described as very put together, intelligent and possessing political knowledge and experience that could prove beneficial to the resistance fighter.

Reuben previously starred on TNT’s Raising the Bar and has appeared on Law & Order: Special Victims Unit and Drop Dead Diva.